In printed wiring boards widely used in electronic equipment, communication instruments, personal computers, and the like, higher density wiring and higher integration progress. With this, excellent characteristics such as heat resistance, low water absorbency, moisture absorption and heat resistance properties, dielectric characteristics, and peel strength are required of metal foil-clad laminates used in printed wiring boards.
On the other hand, cyanate compounds have been known for a long time as raw materials of thermosetting resins having excellent moisture absorption and heat resistance properties, dielectric characteristics, and the like. In recent years, thermosetting resin compositions containing cyanate compounds have been widely used as materials for high function printed wiring boards, such as for semiconductor plastic packages, and the like because cured products having excellent characteristics in electrical characteristics, mechanical characteristics, chemical resistance, adhesiveness, and the like are relatively easily obtained.
For example, thermosetting resin compositions containing bisphenol A-based cyanate compounds are well known. However, cured products thereof may be insufficient in terms of low water absorbency and flame resistance under severe conditions. Therefore, with the aim of further improving characteristics, thermosetting resin compositions using cyanate compounds having other structures are studied.
As those using cyanate compounds having other structures, thermosetting resin compositions containing phenol novolac-based cyanate having a number average molecular weight of 260 to 450 (see Patent Literature 1), thermosetting resin compositions containing a copolymer of bisphenol A-based cyanate and novolac-based cyanate (see Patent Literature 2), and the like are known.
In addition, thermosetting resin compositions containing phenol-modified cyanate oligomers obtained by reacting cyanate compounds with phenol compounds (see Patent Literature 3), thermosetting resin compositions containing biphenyl aralkyl-based cyanate compounds (see Patent Literature 4), and the like are known.